Abstract This is the first competing renewal of a collaborative project between the groups of Dr. Allan Wolkoff and Dr. Ana Maria Cuervo to investigate the role of endocytic/lysosomal processes in liver pathophysiology. During the previous period, we developed technology to dissect the molecular mechanism regulating trafficking of the vesicular components that participate in these processes. We also made the original discovery that endocytic and autophagic pathways are tightly interrelated functionally and that dysfunction of these processes can lead to dysregulation of lipid and carbohydrate metabolism in the liver. We now intend to continue this line of studies focusing on a selective form of autophagy, chaperone-mediated autophagy (CMA) to test our working hypothesis that CMA malfunctioning could contribute to the pathogenesis of metabolic syndrome, non- alcoholic fatty liver disease (NAFLD) and liver fibrosis. We propose that 1) reduced hepatic CMA activity as a result of dietary challenges and aging contributes to accelerate progression of fatty liver disease and that 2) enhancing this form of autophagy could be a successful intervention to prevent progression of fatty liver Disease To test this hypothesis we intend to: 1) determine the molecular basis of dietary-induced hepatic CMA dysfunction both in mouse models and NAFLD patients; 2) characterize the spatiotemporal sequence of CMA changes in the fatty liver and during liver fibrosis; 3) test if genetic or chemical enhancement of CMA is effective in protecting lipid challenged livers against lipotoxicity and disease progression. Significance: This study will elucidate how a functional decline of CMA contributes to fatty liver disease and liver fibrosis. Our findings could help in developing new approaches to protect the liver from lipotoxicity and to reduce progression to liver fibrosis.